The present application claims the benefit of Japanese Patent Application No. 11-326591 which is hereby incorporated by reference.
1. Field of the Invention
The present invention relates to a stereoscopic microscope, and particularly, to a stereoscopic microscope in which a microscope body tube is moved to a sample to be inspected for focusing.
2. Related Background Art
In an ordinary microscope, a focusing operation is conducted by changing a distance between a sample to be inspected and the microscope. In order to change this distance, there is employed either a method in which the position of the sample is fixed and the microscope body tube is motioned (which is called a vertical motion, since in most cases the body tube is motioned vertically), as shown in FIG. 6, or a method in which the microscope is fixed and the sample itself is vertically motioned, as shown in FIG. 7. These methods are employed for a stereoscopic microscope.
A base portion 600 in FIG. 6 is provided with a stage 600a for placing a sample thereon, and in order to inspect details of a sample having certain dimensions, it is inevitable to secure a space for the motion of the sample. For this reason, guide mechanisms 300a and 400a capable of vertical motion are disposed at positions apart from the stage 600a. A fixed stay 400 of the guide mechanisms 300a and 400a is disposed on the base portion 600, and a holding member 300 for holding the body tube 1 of the stereoscopic microscope is disposed on the side of motion of the guide mechanisms 300a and 400a. 
In FIG. 6, in order to conduct a focusing operation, that is, to move the body tube 1 of the microscope vertically, a rack is formed on the guide mechanism 300a, and a pinion 500a for engaging with the rack is formed on a focusing knob 500. The rack and the pinion may be inversely disposed in the same manner.
In case of FIG. 7, in order to move the sample vertically, guide mechanisms 800a and 900a which vertically move are disposed inside the base 600, to be operated by the focusing knob 900. In this case, a microscope body tube 200 is arranged to be secured to a main body 700 of the microscope. For the guide mechanisms 800a and 900a, the rack-and-pinion structure is generally employed. Since the magnification of a stereoscopic microscope is lower than that of an ordinary microscope, and in terms of the working efficiency, the observer often holds a sample directly by his or her own hand and moves the sample for inspection. The sample to be inspected may be a minute part in the industrial field, or may be a plant or a small animal such as an insect. The sample also may be a sample in liquid such as a cultured cell floating in culture solution.
Not a few of such cubic samples have a difference in level (a level difference in the direction of the optical axis of the objective lens) which may reach several tenths millimeters to several millimeters.
In this case, in order to observe the sample in detail, it is required to raise the magnification of the microscope. However, if the magnification is set high, only a several hundredths millimeters of depth of focus can be obtained, so that with respect to the sample having a level difference not smaller than this depth of focus, two positions having such level differences can not be focused at the same time. As a result, it is required to conduct a focusing operation repeatedly for each portion to be observed. Moreover, even within the depth of focus, in order to confirm the best focus condition whenever a portion to be inspected is changed, the focusing operation may be repeatedly conducted.
Consequently, in such a stereoscopic microscope as shown in FIG. 6, (according to the method of vertically moving the body tube 200 of the microscope), it is inevitable to dispose the focusing knob 500 around the guide mechanisms 300a and 400a at a position substantially separated from the stage 600a in the depth direction. Moreover, a large vertical motion stroke is required to cope with a sample having certain height, so that it is required to dispose the focusing knob 500 considerably above the upper surface of the base 600.
When a sample having a level difference is to be observed, since a focusing operation is conducted for each portion to be observed of such sample, it is required to frequently conduct an operation for confirming the position of the focusing knob 500 and an operation for moving the operating hand in an upper depth direction, which is very irksome. Also, to raise the hand upward tires the observer.
On the other hand, in such a stereoscopic microscope as shown in FIG. 7, (according to the focus method of vertically motioning a sample to be inspected), the focusing knob 900 can be easily disposed around the stage 800, which is effective for the above-mentioned problem. However, to move the sample vertically causes undesired movement of the sample itself when the sample is floating in liquid, and disturbs the liquid surface, so as to largely deteriorate the observed image.
If the focusing knob 900 is disposed around the stage 800, and particularly, in an upper part than a surface on which the sample is placed, a probability of unprepared contact between a focus operating unit and the sample becomes high when the samples are exchanged on the stage, which may cause an accident leading to damage of the sample or, in the worst case, damage of the microscope.
In consideration of the problems described above, an object of the present invention is to provide a stereoscopic microscope which is capable of improving the operability thereof and capable of preventing unprepared contact with the focusing member (focusing knob).
According to a main aspect of the present invention, a stereoscopic microscope comprises a body tube provided with an objective lens, a base provided with a stage on which a sample as an object to be inspected is mounted, a guide mechanism for driving the body tube and changing a distance between the body tube and the sample for focusing, a focus driving unit for transmitting a driving force to a movable portion of the guide mechanism, and a focus operating unit which can be operated externally for giving the driving force to the focus driving unit in order to drive the guide mechanism, and is characterized in that the guide mechanism is placed on one end of the base, the focus driving unit is placed inside the base, and the focus operating unit is placed on the other end of the base. As a result, the operability of the stereoscopic microscope at observation is enhanced, so that it is not difficult to conduct the observation with the sample which is not swinging.